Which shield are you using? The WizFi 210 module has four ports to communicate with the MCU, and different shields might use different WizFi module port. SainSmart shield, for example, uses UART (serial) as Uno-WizFi link. This prevents Uno from communicating with your PC, because Uno-PC connection uses the same port. If this is the case with your shield, too, then program the Uno without the WiFi shield, then disconnect from PC, (unplug the power if you are powering the Uno from external power supply, too), connect the shield, and power Uno, but do not connect Uno to PC while the WiFi shield is attached.